Initial research on the process of sharpening ceramic knives as disclosed in U.S. Pat. No. 8,585,462, ('462 Patent), concluded that due to the fracturing of the brittle and fragile ceramic knife edge, to properly develop a factory quality edge, it would require a minimum of three (3) progressive sharpening stages. All of the details of the '462 Patent are incorporated herein by reference thereto.
The (diamond) abrasives grit size would successively be smaller as the ceramic knife is sharpened in stage 1 followed by stage 2 and finished in stage 3. By reducing the grit size of the abrasives in stage 1 and 2 the sizes of the chips in the knife edge would be reduced sufficiently so that the very fine abrasive in stage 3 would be able to remove the remaining small chips and provide a chip free edge.
To further reduce the size of the chips developed in stages 1 and 2, the research concluded that the sharpening process in those two stages should be done by the abrasive moving into the edge, thereby removing ceramic material under compression. By this process the very fine abrasive in stage 3 could remove the small chips. However, to develop a sharp, chip free edge, the direction of the final, finishing stage abrasive would need to move in the opposite direction from stages 1 and 2, thereby moving away from the edge.
Although excellent results could be obtained by this method it provides some drawbacks. First, the requirement to change the direction of the rotation of the abrasive discs presented additional cost, making the manufacture of this sharpener more expensive. Second, the requirement to have at least 3 stages to accomplish the ceramic knife sharpening task, further exacerbated the manufacturing cost. And finally, because of the very small grit size abrasives required in all stages to minimize the chipping process, this sharpener would not be able to sharpen in a reasonably acceptable time, steel knives, which are much more prevalent in homes and stores.
A concern with knife sharpeners, whether for ceramic blades or metal blades, is the difficulty in cleaning or removing swarf created during sharpening from the guide surfaces in the various stages of a sharpener, particularly in the finishing stage.